This invention relates to a method to produce a chemical that has demonstrated activity in the stabilization of elastomeric polymers.
The compounds produced by the process of this invention exhibit synergistic activity with known amine and phenolic antidegradants and the combination provides a long lasting and persistent antioxidative protection to elastomeric polymers.
U.S. Pat. Nos. 4,241,217, 4,301,298 and 4,125,515 disclose combinations of esters and amines wherein an ester such as 3,6,9-trioxaundecane-1,11-bis(3-n-dodecylthiopropionate) is combined with conventional amine antioxidants (such as N,N'-diphenyl-para-phenylenediamine or polymer bound antidegradants such as N-(4-anilinophenyl)methacrylamide) to produce improved antioxidant systems for elastomeric-type polymers. A process for the preparation of the esters is also illustrated in U.S. Pat. Nos. 3,629,194 and 3,758,549.
U.S. Pat. No. 4,216,116 discloses a combination of a phenolic antioxidant with an ester such as 3,6,9-trioxaundecamethylene bis[3-(dodecylthio)propionate to stabilize polymers against oxidative degradation.
These esters or synergists are conventionally prepared by reacting a suitable thiol with an ester of acrylic or methacrylic acid in the presence of a basic catalyst such as KOH or benzyl trimethyl ammonium hydroxide. These synergists have also been prepared by reacting a suitable acid with an alcohol in a known acid catalyzed esterification procedure as described in U.S. Pat. No. 2,601,063.
A previously used process to prepare these synergists involves the initial reaction of a suitable thiol with a lower alkyl ester of acrylic or methacrylic acid. The alkylthiopropionate ester is then esterified with a high molecular weight glycol.
U.K. Patent 1,047,389 describes a process for the manufacture of dialkyl tin oxides and hydroxides. The dialkyl tin oxides are useful as intermediates in the preparation of PVC stabilizers, bacteriocides, fungicides and molluscicides. This British patent describes a process for the preparation of alkyl tin oxides which comprises reacting tin with an alkyl or alkenyl halide in the presence of a catalyst and an organic compound which is a Lewis base.
U.S. Pat. No. 2,720,507 describes the use of an organometallic tin catalyst for the preparation of polyesters. This patent discloses tin compounds, such as dialkyl tin oxides, as a condensing agent in the preparation of high melting linear polyesters. This patent describes a process wherein carboxylic acids are esterified by reaction with esters in the presence of a catalytic amount of a tin halide catalyst, the reaction being effected at temperatures ranging from 0.degree. C. to about 150.degree. C.
U.S. Pat. No. 4,206,143 discloses a method for making N-substituted acrylamide or N-substituted methacrylamides which comprises reacting an alkyl ester of acrylic acid or of methacrylic acid with an aliphatic amine or with an aromatic amine at a temperature between 50.degree. C. and 180.degree. C. in the presence of a catalytic amount of a dialkyl tin oxide.
U.S. Pat. No. 4,492,801 describes a one-step process for the preparation of N-substituted (meth)acrylamides from the reaction of a (meth)acrylate ester and an amine over a catalytic amount of a metal alkoxide catalyst. These catalysts, such as stannous dimethoxide, provide high selectivity to the N-substituted (meth)acrylamides and little selectivity to the Michael addition adduct which would predominate in the absence of these catalysts.
None of the prior art discloses or suggests that dialkyl tin oxides can be used to enhance the reaction between an alkyl thiopropionate and a glycol to produce compounds such as 3,6,9-trioxaundecane-1,11-bis(3-n-dodecylthiopropionate).